“He had the folly to believe that to be feared is glory.”

Queen Mary Stuart as portrayed in Bothwell. Act I. Sc. 3.
Bothwell : A Tragedy (1874)

Source: Unbroken: A World War II Story of Survival, Resilience, and Redemption

Letter to William Eustis http://books.google.com/books?id=S088AAAAIAAJ&pg=PA319 (22 June 1809), published in Writings of John Quincy, Adams (1914), The Macmillan company.
Variant: All men profess honesty as long as they can. To believe all men honest would be folly. To believe none so is something worse.

A Lost Lady (1923), Part II, Ch. 9
Context: He had seen the end of an era, the sunset of the pioneer. He had come upon it when already its glory was nearly spent. So in the buffalo times a traveller used to come upon the embers of a hunter's fire on the prairies, after the hunter was up and gone; the coals would be trampled out, but the ground was warm, and the flattened grass where he had slept and where his pony had grazed, told the story.
This was the very end of the road-making West; the men who had put plains and mountains under the iron harness were old; some were poor, and even the successful ones were hunting for rest and a brief reprieve from death. It was already gone, that age; nothing could ever bring it back. The taste and smell and song of it, the visions those men had seen in the air and followed, — these he had caught in a kind of afterglow in their own faces, — and this would always be his.

The Notebooks of Leonardo da Vinci (1883), XIX Philosophical Maxims. Morals. Polemics and Speculations.

History and Utopia (1960)

Source: Vanity of Human Wishes (1749), Line 316